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CMMG fixed ejector kit not reliable with FRT (Page 2 of 2)
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If that guy removed the buffer retaining pin, I bet that makes for a fun time closing the upper and lower, and it being eventful when opening it. I did contemplate welding up and then re machining the channel to narrow it. In reality, all you would need to weld up is just the very end where it hit the lever. Then mill it back out to be just the width it needs to be. |
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Originally Posted By Jeeps-And-Guns: If that guy removed the buffer retaining pin, I bet that makes for a fun time closing the upper and lower, and it being eventful when opening it. Again, I am in FL where FRT's / SS's are illegal so I have no firsthand experience with any of them...but another customer sent me pics of I think an Arcfire? that is really narrow, more narrow than the Colt carrier.....I think that setup sits off the centerline to not be a problem. |
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Ok, to update a little. Turns out the atrius lever was hitting the upper. I found the marks on it that I had not seen before. I clearanced the upper and then ordered a new lever. Once the new lever came in, I found the old one was bent. I installed the new lever and finally had a chance to try it out yesterday. No dice. It ran perfectly in semi auto, but would choke after a couple round in forced reset. The lever was still getting stuck under the BCG. I just happened to have another AR I was testing and it has a arc-fire, but the same H3 and tubbs spring. I swapped the 9mm upper onto it and gave it a try. It actually ran perfectly. I had tried a arc fire once before and it did not run, so not sure why it is now. I swapped in that exact trigger and arc fire into the 9mm that night and will give it a try hopefully next weekend. |
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Ok, I took the 9mm and swapped in the cut SSA trigger and arc-fire. I put 200 rounds through it today and it ran flawlessly. Still too early to tell for sure, but it seems to be doing great. So as it sets right now: Spikes lower receiver CMMG RDB 16in barrel, fixed ejector upper/bcg. SSA trigger, cut for a ARC-fire, and arc fire V1 Tromix steel H3 FRT buffer. Tubbs flat wire buffer spring. So for me I am done with the JRC buffer tubes and kynshot buffers. My honest opinion they did not offer much of a benefit to outweigh using non standard parts. With the standard buffer tube and buffer, I can still use this lower with other standard uppers if I want. Where if I was using the JRC and kynshot, I could not. I will probably list them in the EE when I get a little free time. |
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Originally Posted By Jeeps-And-Guns: Ok, I took the 9mm and swapped in the cut SSA trigger and arc-fire. I put 200 rounds through it today and it ran flawlessly. Still too early to tell for sure, but it seems to be doing great. So as it sets right now: Spikes lower receiver CMMG RDB 16in barrel, fixed ejector upper/bcg. SSA trigger, cut for a ARC-fire, and arc fire V1 Tromix steel H3 FRT buffer. Tubbs flat wire buffer spring. So for me I am done with the JRC buffer tubes and kynshot buffers. My honest opinion they did not offer much of a benefit to outweigh using non standard parts. With the standard buffer tube and buffer, I can still use this lower with other standard uppers if I want. Where if I was using the JRC and kynshot, I could not. I will probably list them in the EE when I get a little free time. I can use the JRC and Kynshot equipped M16 lowers with both 9mm and 556 but only if I use my Surefire OBC carrier in 556. All that said, I find that the magnetic buffers I've made are the smoothest in full auto, producing the slowest cyclic rates and also the lowest amount of reciprocating mass. My magnetic weighs in at 3.7oz and my lightened carrier is 9oz. So only 12.7oz of reciprocating mass and I'm just under 600RPM which no other SMG on the planet can do both. I'm running this in an A5 length buffer tube in both 9mm (CMMG RDB) and 556 with extended stroke. |
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Having similar issues with my CMMG retrofit kit built upper. I biought a 5" barrel with single feed lip from Amphibian. I also cxhanged to the buffer set up Amphibian recommended (A5 tube, Warthog flat spring and Kynshot RB5007 buffer). With the binary trigger, it runs perfect on semi and binary mode. I then changed out the binary for an ARCFire V2 and it's a big no go. I couldn't even get the 300 Blk upper to run in that combo. My 300 is horribly over gassed (will cycle subs without suppressor). I put on a Superlative Arms AGB, tuned it in semi-auto mode then tried FRT. Wouldn't even feed a round (BCG is short stroking), so I started turning up the gas and back at full over gassed wide open, still wouldn't run. So, I removed the A5 tube, put a standard carbine tube back on, standard carbine spring and a sliding weight H2 buffer I bought from Tromix. Still a no go with the 9mm. If I start with 10+ rounds (Magpul 30-round mag with an Endomag insert), it'll sometimes not feed at all, or it'll double feed. When the round count gets down to 5-6 rounds, it'll start to run, but only go 3-4 rounds and stop. Releasing the trigger let's it run another 3-4 rounds before next stoppage. It's acting like it's still short stroking. Unfortunately, I am unable to test the 300 upper with the new buffer set up as last time I ran it, it blew the case neck off one of the rounds (my fault as I make my own 300 brass from 223/5.56 brass and was messing with a neck turner, apparently I went too far down the neck and into the shoulder some). Since then, the 300 will not fire. It doesn't even dimple the primer. Firing pin sticks out the right amount, so I suspect it's something with the extractor claw or ejector plunger keeping the round from seating fully against the bolt face. Will have to tear it down when I get a chance. Either way, I really want it to work with the 9mm build and so far it's been frustrating. For S&G's, we put the 18" 223 Wylde upper on the FRT lower (with the carbine tube, spring and H2 buffer) and mag dumped 18 rounds and it ran perfect. Brass ejection was perfect at 3:30-ish, and put them all in a neat little pile. So, the trigger is fine, the lower is fine, it's just got to be something with the buffer set up with the 9mm. I'm thinking about just putting the original carbine buffer in it and see what happens. It's not a sliding weight buffer, but I still think that the energy the trigger reset is robbing from the BCG doesn't leave enough to cycle the buffer back far enough. It still acts like it's short stroking. Here's the 18" 223 Wylde upper in action:  18" 223 Wylde |
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Originally Posted By EDL: Having similar issues with my CMMG retrofit kit built upper. I biought a 5" barrel with single feed lip from Amphibian. I also cxhanged to the buffer set up Amphibian recommended (A5 tube, Warthog flat spring and Kynshot RB5007 buffer). With the binary trigger, it runs perfect on semi and binary mode. I then changed out the binary for an ARCFire V2 and it's a big no go. I couldn't even get the 300 Blk upper to run in that combo. My 300 is horribly over gassed (will cycle subs without suppressor). I put on a Superlative Arms AGB, tuned it in semi-auto mode then tried FRT. Wouldn't even feed a round (BCG is short stroking), so I started turning up the gas and back at full over gassed wide open, still wouldn't run. So, I removed the A5 tube, put a standard carbine tube back on, standard carbine spring and a sliding weight H2 buffer I bought from Tromix. Still a no go with the 9mm. If I start with 10+ rounds (Magpul 30-round mag with an Endomag insert), it'll sometimes not feed at all, or it'll double feed. When the round count gets down to 5-6 rounds, it'll start to run, but only go 3-4 rounds and stop. Releasing the trigger let's it run another 3-4 rounds before next stoppage. It's acting like it's still short stroking. Unfortunately, I am unable to test the 300 upper with the new buffer set up as last time I ran it, it blew the case neck off one of the rounds (my fault as I make my own 300 brass from 223/5.56 brass and was messing with a neck turner, apparently I went too far down the neck and into the shoulder some). Since then, the 300 will not fire. It doesn't even dimple the primer. Firing pin sticks out the right amount, so I suspect it's something with the extractor claw or ejector plunger keeping the round from seating fully against the bolt face. Will have to tear it down when I get a chance. Either way, I really want it to work with the 9mm build and so far it's been frustrating. For S&G's, we put the 18" 223 Wylde upper on the FRT lower (with the carbine tube, spring and H2 buffer) and mag dumped 18 rounds and it ran perfect. Brass ejection was perfect at 3:30-ish, and put them all in a neat little pile. So, the trigger is fine, the lower is fine, it's just got to be something with the buffer set up with the 9mm. I'm thinking about just putting the original carbine buffer in it and see what happens. It's not a sliding weight buffer, but I still think that the energy the trigger reset is robbing from the BCG doesn't leave enough to cycle the buffer back far enough. It still acts like it's short stroking. Here's the 18" 223 Wylde upper in action:  https://www.youtube.com/shorts/p0r4vUwaQDU I'm sure with mine being 16in and yours being 5in is going to change a lot of things. You might try a standard carbine buffer with sliding steel weights. I have the tubbs lightweight buffer spring I had bought and tried, that I am no longer using. You are welcome to it if you want to try it, just pm me your address and I can send it out. It can be very frustrating getting some of these frt's to run. I had tried my 9mm in the past with a arc fire and it would not run. But as of now, it is running fine. I'm going to try running a couple hundred more round through it this weekend and see how it does. |
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Originally Posted By EDL: Having similar issues with my CMMG retrofit kit built upper. I biought a 5" barrel with single feed lip from Amphibian. I also cxhanged to the buffer set up Amphibian recommended (A5 tube, Warthog flat spring and Kynshot RB5007 buffer). With the binary trigger, it runs perfect on semi and binary mode. I then changed out the binary for an ARCFire V2 and it's a big no go. I couldn't even get the 300 Blk upper to run in that combo. My 300 is horribly over gassed (will cycle subs without suppressor). I put on a Superlative Arms AGB, tuned it in semi-auto mode then tried FRT. Wouldn't even feed a round (BCG is short stroking), so I started turning up the gas and back at full over gassed wide open, still wouldn't run. So, I removed the A5 tube, put a standard carbine tube back on, standard carbine spring and a sliding weight H2 buffer I bought from Tromix. Still a no go with the 9mm. If I start with 10+ rounds (Magpul 30-round mag with an Endomag insert), it'll sometimes not feed at all, or it'll double feed. When the round count gets down to 5-6 rounds, it'll start to run, but only go 3-4 rounds and stop. Releasing the trigger let's it run another 3-4 rounds before next stoppage. It's acting like it's still short stroking. Unfortunately, I am unable to test the 300 upper with the new buffer set up as last time I ran it, it blew the case neck off one of the rounds (my fault as I make my own 300 brass from 223/5.56 brass and was messing with a neck turner, apparently I went too far down the neck and into the shoulder some). Since then, the 300 will not fire. It doesn't even dimple the primer. Firing pin sticks out the right amount, so I suspect it's something with the extractor claw or ejector plunger keeping the round from seating fully against the bolt face. Will have to tear it down when I get a chance. Either way, I really want it to work with the 9mm build and so far it's been frustrating. For S&G's, we put the 18" 223 Wylde upper on the FRT lower (with the carbine tube, spring and H2 buffer) and mag dumped 18 rounds and it ran perfect. Brass ejection was perfect at 3:30-ish, and put them all in a neat little pile. So, the trigger is fine, the lower is fine, it's just got to be something with the buffer set up with the 9mm. I'm thinking about just putting the original carbine buffer in it and see what happens. It's not a sliding weight buffer, but I still think that the energy the trigger reset is robbing from the BCG doesn't leave enough to cycle the buffer back far enough. It still acts like it's short stroking. Here's the 18" 223 Wylde upper in action: https://www.youtube.com/shorts/p0r4vUwaQDU Speaking to your 9mm. Is the endomag basically new? I pose that question for 2 reasons. First, the problem you describe is a feeding problem. Second, my personal experience with endomags is "temporary" success followed by not good enough for feeding in semi by the next range trip (30 days loaded killed 3 of mine off and made for an embarassing range trip). My endomag fix was to move to colt pattern and CZ pattern mags in the two lowers I had set up for endo/exomags. |
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Originally Posted By dredeagle: Speaking to your 9mm. Is the endomag basically new? I pose that question for 2 reasons. First, the problem you describe is a feeding problem. Second, my personal experience with endomags is "temporary" success followed by not good enough for feeding in semi by the next range trip (30 days loaded killed 3 of mine off and made for an embarassing range trip). My endomag fix was to move to colt pattern and CZ pattern mags in the two lowers I had set up for endo/exomags. The Endomag is relatively new, it's had at least a couple hundred rounds put through it. I think the feeding issues and the FRT mode stoppages are two different things. When it doesn't misfeed and is running, FRT mode is only good for a few rounds then it stops. I can let off the trigger which resets it and pull it again and go through several more rounds before it stops again (so it's not a misfeed since there is one in the chamber). It's like the trigger isn't getting reset because the BCG isn't going back far enough to reset the trigger. I have a shim kit that AS Designs sent, they said it will change the timing (will cause the trigger reset to occur sooner on lever travel), but I have yet to put them in, partly because I just got the new H2 buffer and changed the set up and needed to try it, and partly because I haven't looked to see where the shims go exactly. Since the 300 has a bit more oomph to it and having the AGB, if I can get the 9mm to run, I should be able to tune the 300 to run with whatever buffer works on the 9mm. Don't the Colt and CZ mags require a 9mm specific lower? I'm not against SBRing another lower and making the 9mm and the 300 two separate set ups, but I like to tinker and having two uppers that'll run on one lower is cheaper and easy enough to swap uppers, so why not try. I'm just scratching my head because I see others with very short barrels on CMMG RDB uppers running H3 buffers and they rip. Just can't, at this point, figure out why mine isn't running with a lighter H2 buffer. Guess I'll try another spring/buffer combo. Also thought about getting an Exomag and see if it works better than the Endomag on the feed issue (I think I read somewhere that CMMG or someone else is now making a 9mm mag also for standard lowers), which only really happens when I put more than about 10 rounds in the mag. Less than that, I get no feed issues. I could get that Odin Works adjustable weight buffer kit and that would let me change weight up and down as needed to see what works (if it will). I dunno at this point. |
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I have been running the CMMG 33 round mags and so far they work great. I had been using the endo mags with no issues, and the only reason I stopped was because I could mod them to be able to hold 9x23 win, and I built a 9x23 upper. So instead of buying more endo mags and having to use more p-mag bodies, I decided to just bey dedicated mags. I was debating between the exo mags and the cmmg, and ended up going with the cmmg. |
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Did you put the shims in yours too? I think I'll try that next and see what, if any, difference it makes. Might order one of the CMMG mags and one of the Endomags to see if it makes any difference. It could be the magpul mag itself causing issues with the Endomag insert. The mag has been around a while and used in other stuff. I originally bought it some years ago when I first built the 300. The trick back then was to shave down the ribs inside so it would feed 300, but I never shaved it and only ran 5.56 in it. Maybe a purpose built mag will help. Looked around and, huh, never knew Tractor Supply sold gun parts, lol. https://www.tractorsupply.com/tsc/product/cmmg-33-round-9mm-magazine-for-ar-15-black-polymer |
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Originally Posted By EDL: Did you put the shims in yours too? I think I'll try that next and see what, if any, difference it makes. Might order one of the CMMG mags and one of the Endomags to see if it makes any difference. It could be the magpul mag itself causing issues with the Endomag insert. The mag has been around a while and used in other stuff. I originally bought it some years ago when I first built the 300. The trick back then was to shave down the ribs inside so it would feed 300, but I never shaved it and only ran 5.56 in it. Maybe a purpose built mag will help. Looked around and, huh, never knew Tractor Supply sold gun parts, lol. https://www.tractorsupply.com/tsc/product/cmmg-33-round-9mm-magazine-for-ar-15-black-polymer Shims in what? The arc fire, or are you talking about the mags? I did not use the shim in the arc fire, and I did not know about any shims for the mags. |
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Shims in the ARCFire. Someone here mentioned them before and apparently that fixed theirs to get it to run right. As I posted above when we put the 18" 5.56 upper on the lower, it runs like a top, so it's not the lower or the trigger. It has to be a combo of the buffer and the reduced recoil of 9mm and 300 subsonics. I'm going to put the shims in (have to find out where they go/how to install them) and try it. If that's still a no go then I'm going to put the basic carbine buffer in and see how it goes. I'll order a CMMG and Exo mag in the mean time too. After all that, if it still doesn't run, then I'm going to get the 300 working and I'll SBR a 9mm specific lower and see if I can get the 9mm to run on that later. It's not a huge deal really. I would like to get the 9mm to work since running in FRT mode on that is a lot cheaper than burning through 300 Blk :-) I still have a fair bit of powder and whatnot that I bought a few years ago when prices were much better. Right now I'm reloading 115 grain 9mm for about 15 cents a round. I just bought some 147 grain 9mm bullets, and even with the slightly higher prices on those, I'll still be under 20 cents a round. |
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I tried installing one of those shims in my 16in 223 build to try and get it running, and it would not work. As soon as I put the shim in and tightened down the selector screw, the thing locked up. You could not move it between positions. Loosen the scew a little and it would move, but tighten it back down and it would lock up. It was the correct size shims, ordered directly from the link ASD posted, and it was placed in the correct spot. So far I have not read of anyone else having this issue. No idea why I did. |
CMMG fixed ejector kit not reliable with FRT (Page 2 of 2)
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